The nation can begin to address the risks of climate change while avoiding harm to the economy, senators said Wednesday in unveiling anti-pollution legislation.

The bill would establish a mandatory cap on carbon dioxide emissions from power plants, refineries and industrial plants but allow companies to trade emission credits and avoid making emissions cuts if the costs become too high.

Sen. Jeff Bingaman, D-N.M., one of the bill's chief sponsors, called it a "strong and balanced approach ... while protecting the American economy." It also includes incentives aimed at spurring other nations such as China to address climate change.

The bill is one of five that are being considered in the Senate to tackle global warming. It is expected to be the one most closely embraced by industry, including companies that would be most affected.

Joining Bingaman at a news conference Wednesday to announce the legislation were executives of some of the country's biggest coal-burning utilities and unions representing autoworkers and coal miners.

It's a "balanced and fair approach that recognizes that economic development and environmental progress can and should go hand in hand," said Richard Trumka, secretary-treasurer of the AFL-CIO.

Among others at the news conference were chief executives of Duke Energy Co. and American Electric Power, two of the biggest operators of coal-burning power plants that emit millions of tons of carbon dioxide annually.

The bill would establish carbon emission limits throughout industry to assure that the releases do not grow significantly over the next two decades. Carbon emissions would have to be at 2006 levels in 2030, instead of growing at the rate of more than 1 percent a year as is projected without emissions caps.

But many environmentalist — and a number of senators — argue that more stringent restrictions are needed to prevent the kind of warming that will result in dangerous climate change, ice cap melting and sea level rises.

Several bills have been introduced that would require a reduction in greenhouse gases of as much as 80 percent from what they were in 1990, when emissions were considerably less than even today.

Bingaman said his bill has a goal of cutting carbon dioxide releases by 60 percent from 2006 levels by mid-century. But he acknowledged even that would require a future president — as is allowed in the bill — to ratchet up emission controls.

"I understand there are some who would like more aggressive targets, but we're trying to put together legislation that will pass," said Bingaman, alluding to the difficulty of getting climate legislation passed without broad support. Any bill is likely to require 60 votes in the Senate, where it is almost assured of attracting a filibuster threat.

Environmentalists are most concerned about the "safety valve" included in Bingaman's bill that would allow a company to avoid making an emission reduction if the cost exceeds a certain amount — $12 a ton of carbon dioxide initially and increasing over the years.

"The safety valve is a dangerous kill switch that could turn off the whole program," said Steve Cochran, climate campaign director for Environmental Defense, an advocacy group that has strongly supported the "cap-and-trade" approach for dealing with global warming.

Still, said Cochran, the bill reflects the growing support for mandatory limits on carbon dioxide and other greenhouse gases linked to global warming.